Development and Contributing



This document describes the development process of KIWI and how you can be part of it. This description applies to version 9.17.39.

The core appliance builder is developed in Python and follows the test driven development rules.

If you want to implement a bigger feature, consider opening an issue on GitHub first to discuss the changes. Or join the discussion in the #kiwi channel on

Fork the upstream KIWI repository

  1. On GitHub, navigate to:

  2. In the top-right corner of the page, click Fork.

Create a local clone of the forked KIWI repository

$ git clone

$ git remote add upstream

Install Required Operating System Packages

KIWI requires the following additional packages which are not provided by pip:

  • XML processing libraries: libxml2 and libxslt (for lxml)

  • Python header files (for xattr), usually provided by a package called python-devel or python3-devel

  • The enchant spell checking library

  • gcc compiler and glibc-devel header files

  • The ShellCheck script linter.

  • A manipulation program for ISO images, either: xorriso (preferred) or genisoimage.

A full LaTeX installation is required to build the PDF documentation 1.

On SUSE based systems run:

$ zypper install --no-recommends \
      python3-devel libxml2-devel libxslt-devel glibc-devel gcc \
      trang xorriso \
      texlive-fncychap texlive-wrapfig texlive-capt-of \
      texlive-latexmk texlive-cmap texlive-babel-english \
      texlive-times texlive-titlesec texlive-tabulary texlive-framed \
      texlive-float texlive-upquote texlive-parskip texlive-needspace \
      texlive-makeindex-bin texlive-collection-fontsrecommended \

On Fedora the following commands should install the required packages:

$ dnf install python3 python3-devel 'python3dist(pip)' \
   'python3dist(tox)' make gcc which xz xorriso libxml2-devel \
   libxslt-devel enchant genisoimage ShellCheck
$ # LaTeX packages
$ dnf install latexmk texlive-cmap texlive-metafont texlive-ec \
   texlive-babel-english texlive-fncychap texlive-fancyhdr \
   texlive-titlesec texlive-tabulary texlive-framed texlive-wrapfig \
   texlive-parskip texlive-upquote texlive-capt-of texlive-needspace \
   texlive-makeindex texlive-times texlive-helvetic texlive-courier \
   texlive-gsftopk texlive-updmap-map texlive-dvips

Create a Python Virtual Development Environment

We recommend to setup a Python virtualenv for development. For Python 3 python3 -m venv is used, as it is bundled with Python itself (see for details). For Python 2.7, use virtualenv, which is provided via pip or as an extra package by your favorite Linux distribution.

The following commands initializes a development environment for Python 3:

$ python3 -m venv .env3
$ source .env3/bin/activate
$ pip install -r
$ python3 develop

The develop target of the script automatically creates the application entry point called kiwi-ng-3, which allows you to call the your modified version of KIWI from inside the virtual environment:

$ kiwi-ng-3 --help


The virtualenv’s $PATH will not be taken into account when calling KIWI via sudo! Use the absolute path to the KIWI executable to run an actual build using your local changes:

$ sudo $PWD/.env3/bin/kiwi-ng-3 system build ...

In order to leave the development mode call:

$ deactivate

To resume your work, cd into your local Git repository and call:

$ source .env3/bin/activate

Running the Unit Tests

We use tox to run the unit tests. Tox sets up its own virtualenvs inside the .tox directory for multiple Python versions and should thus not be invoked from inside your development virtualenv.

Before submitting your changes via a pull request, ensure that all tests pass and that the code has the required test coverage via the command:

$ tox

We also include pytest-xdist in the development virtualenv which allows to run the unit tests in parallel. It is turned off by default but can be enabled via:


where you can insert an arbitrary number as NUMBER_OF_PROCESSES (or a shell command like $(nproc)). Note that the double quotes around -n NUMBER_OF_PROCESSES are required (otherwise tox will consume this command line flag instead of forwarding it to pytest).

The previous call would run the unit tests for different Python versions, check the source code for errors and build the documentation.

If you want to see the available targets, use the option -l to let tox print a list of them:

$ tox -l

To only run a special target, use the -e option. The following example runs the test cases for the Python 3.7 interpreter only:

$ tox -e unit_py3_7

Create a Branch for each Feature or Bugfix

Code changes should be done in an extra Git branch. This allows for creating GitHub pull requests in a clean way. See also: Collaborating with issues and pull requests

$ git checkout -b my-topic-branch

Make and commit your changes.


You can make multiple commits which is generally useful to give your changes a clear structure and to allow us to better review your work.


Your work is important and must be signed to ensure the integrity of the repository and the code. Thus we recommend to setup a signing key as documented in Signing Git Patches.

$ git commit -S -a

Run the tests and code style checks. All of these are also performed by the Travis CI and GitLab CI integration test systems when a pull request is created.

$ tox

Once everything is done, push your local branch to your forked repository and create a pull request into the upstream repository.

$ git push origin my-topic-branch

Thank you much for contributing to KIWI. Your time and work effort is very much appreciated!

Coding Style

KIWI follows the general PEP8 guidelines with the following exceptions:

  • We do not use free functions at all. Even utility functions must be part of a class, but should be either prefixed with the @classmethod or @staticmethod decorators (whichever is more appropriate).

  • Do not set module and class level variables, put these into the classes’ __init__ method.

  • The names of constants are not written in all capital letters.

  • We do not use type hints (yet) as the current code base needs to maintain Python 2 compatibility.


KIWI uses Sphinx for the API and user documentation.

In order to build the HTML documentation call:

tox -e doc

or to build the full documentation (including a PDF generated by LaTeX 3):

tox -e packagedoc

Document all your classes, methods, their parameters and their types using the standard reStructuredText syntax as supported by Sphinx, an example class is documented as follows:

class Example(object):
    **Example class**

    :param str param: A parameter
    :param bool : Source file name to compress
    :param list supported_zipper: List of supported compression tools
    :attr Optional[str] attr: A class attribute
    def __init__(self, param, param_w_default=False):
        self.attr = param if param_w_default else None

    def method(self, param):
        A method that takes a parameter.

        :param list param: a parameter
        :return: whether param is very long
        :rtype: bool
        return len(param) > 50

Try to stick to the following guidelines when documenting source code:

  • Classes should be documented directly in their main docstring and not in __init__.

  • Document every function parameter and every public attribute including their types.

  • Only public methods should be documented, private methods don’t have to, unless they are complex and it is not easy to grasp what they do (which should be avoided anyway).

Please also document any user-facing changes that you implementing (e.g. adding a new build type) in the user documentation, which can be found in doc/source. General documentation should be put into the working_with_kiwi/ subfolder, whereas documentation about more specialized topics would belong into the building/ subfolder.

Adhere to a line limit of 75 characters when writing the user facing documentation 2.

Additional Information

The following sections provides further information about the repository integrity, version, package and documentation management.

Signing Git Patches

To ensure the integrity of the repository and the code base, patches sent for inclusion should be signed with a GPG key.

To prepare Git to sign commits, follow these instructions:

  1. Create a key suitable for signing (it is not recommended to use existing keys to not mix it with your email environment):

    $ gpg2 --expert --full-gen-key
  2. Either choose a RSA key for signing (option (4)) or an ECC key for signing (option (10)). For a RSA key choose a key size of 4096 bits and for a ECC key choose Curve 25519 (option (1)). Enter a reasonable validity period (we recommend 2 to 5 years). Complete the key generation by entering your name and email address.

  3. Add the key ID to your git configuration, by running the following git config commands:

    $ git config --local user.signingkey $YOUR_SIGN_KEY_ID
    $ git config --local commit.gpgSign true

    Omitting the flag --local will make these settings global for all repositories (they will be added to ~/.gitconfig). You can find your signkey’s ID via:

    $ gpg2 --list-keys --keyid-format long $YOUR_EMAIL
    pub   rsa4096/AABBCCDDEEFF0011 2019-04-26 [S] [expires: 2021-04-16]
    uid                 [ultimate] YOU <$YOUR_EMAIL>

    The key’s ID in this case would be AABBCCDDEEFF0011. Note that your signkey will have only a [S] after the creation date, not a [SC] (then you are looking at your ordinary GPG key that can also encrypt).

Bumping the Version

The KIWI project follows the Semantic Versioning scheme. We use the bumpversion tool for consistent versioning.

Follow these instructions to bump the major, minor, or patch part of the KIWI version. Ensure that your repository is clean (i.e. no modified and unknown files exist) beforehand running bumpversion.

  • For backwards-compatible bug fixes:

    $ bumpversion patch
  • For additional functionality in a backwards-compatible manner. When changed, the patch level is reset to zero:

    $ bumpversion minor
  • For incompatible API changes. When changed, the patch and minor levels are reset to zero:

    $ bumpversion major

Creating a RPM Package

We provide a template for a RPM spec file in package/python-kiwi-spec-template alongside with a rpmlint configuration file and an automatically updated python-kiwi.changes.

To create the necessary files to build a RPM package via rpmbuild, run:

$ make build

The sources are collected in the dist/ directory. These can be directly build it with rpmbuild, fedpkg, or submitted to the Open Build Service using osc.


Sphinx requires a plethora of additional LaTeX packages. Unfortunately there is currently no comprehensive list available. On Ubuntu/Debian installing texlive-latex-extra should be sufficient. For Fedora, consult the package list from .gitlab-ci.yml.


Configure your editor to automatically break lines and/or reformat paragraphs. For Emacs you can use M-x set-fill-column RET 75 and M-x auto-fill-mode RET for automatic filling of paragraphs in conjunction with M-x fill-paragraph (usually bound to M-q) to reformat a paragraph to adhere to the current column width. For editing reStructuredText we recommend rst-mode (built-in to Emacs since version 23.1). Vim users can set the text width via :tw 75 and then use the commands gwip or gq.


Requires a full LaTeX installation.